(A) Western blot analysis for detection of virion-associated antigen of HHV-6. Proteins were subjected to SDS-polyacrylamide gel electrophoresis and transferred onto a nitrocellulose filter. The proteins were reacted with a monoclonal antibody C3 108-103, followed by incubation with peroxidase-labeled antimouse antibody. The blots were developed by the enhanced chemiluminescence method. A 101-kD band is seen in lane 1. Positions of weight markers are indicated on the left. (B) RT-PCR analysis for detection of the immediate-early gene transcript of HHV-6. Isolated RNAs were used for cDNA synthesis and the cDNAs were PCR-amplified with primer pair 3 in the region corresponding to the immediate-early gene. The expected product of 553 bp is seen in lane 1. All cDNAs were subjected in parallel to amplification of the housekeeping gene β-actin, which was expressed at a comparable amount in all samples. Lane 1, HHV-6–infected MT-4 cells; lane 2, Akata cells; lane 3, Katata cells; lane M, φX174/ HincII-cut DNA size marker.